Manufacture of sealing closures for a telecommunications cable splice

ABSTRACT

Making a gas pressurizable closure for a splice region of a telecommunications cable in which plastic ends of the closure are molded in position by locating molds for the ends in axially spaced-apart positions one at each side of the splice region. While the cable is allowed to follow its natural path through and between the molds, the molds are held fixed relative to one another and aligned with one another and the plastic ends are molded. A shroud means of the closure is then located between and sealed to the plastic ends with the cable still following its natural path.

This invention relates to the manufacture of sealing closures fortelecommunications cable splices.

When installing a telecommunications cable system, it is conventionalpractice to splice together conductors of succeeding cables and also tosplice together conductors of a cable with other conductors of branchcables which lead from it. Such branch cables may be in the form of dropwires for connection to customers' premises or cables having fewer pairsof conductors than the main cable and provided for connecting telephoneequipment in a localized area with the main cable. The cables need to beopened for any splicing operation between conductors and, subsequent tothe splicing operation, it is necessary to seal the spliced region fromambient atmosphere to prevent moisture from contacting the splicedconductors. One effective method of sealing spliced together conductorsis as described in U.S. Pat. No. 4,322,573 granted Mar. 30, 1982 to L.J. Charlebois and entitled "Encapsulation of Telecommunications CableSplices". That particular patent concerns the wrapping of overlappingand contacting windings of sealing tape around the connections of thebared conductor ends and then enclosing the splices by injection moldingan encapsulation of molten plastic material. This encapsulation ismolded around the sealing tape wrapping so as to encapsulate each spliceand to soften the sealing tape to merge it into a single mass so as tocause the mass to completely enclose the conductor ends and connectionsand to provide a seal at each splice. This particular arrangement ofsealing closure is for use with unpressurized cable.

In U.S. Pat. No. 4,570,032, issued Feb. 2, 1986 for an inventionentitled "Sealing Enclosure For A Cable Splice" and in the names of L.J. Charlebois and K. H. Dick, a method is described for providing asealing closure in which a new type of seal is used between the closureand cable jacket. In one embodiment as described in that application, asealing closure is described for a splice region of a gas pressurizablecable. A similar embodiment is described in U.S. Pat. No. 4,581,480issued Apr. 8, 1986 in the name of L. J. Charlebois and entitled "CableSplice Closure and Strain Relief".

A problem concerns the making of a gas pressurizable closure for asplice region as described for instance in the above-mentioned U.S. Pat.No. 4,581,480. As described in that patent application, plastic ends ofthe closure are molded in spaced positions before bridging them with ashroud means which is sealed around the periphery of the ends andbridges the splice region. This operation normally takes place in thefield and it is in these surroundings that the ends are molded in theirrespective positions. Of course, in an in-field situation, the cablepath has already been determined because of the manner in which it waspreviously laid. It has been considered necessary to remove, as far aspossible, any slight curvature in the natural path of the cable acrossthe splice region so as to axially align the ends before locating theshroud means in position. However any tendency for the cable to returntowards such a curved shape may distort the assembled closure and causeseal breakage between the shroud means and the plastic ends.

The present invention provides a method of overcoming the aboveproblems.

Accordingly, in a method of molding plastic ends for a gas pressurizableclosure for a splice region of a telecommunications cable in which theclosure has axially spaced molded plastic ends and a bridging shroudmeans the method including molding the ends in position by disposing twomolds for the ends in axially spaced-apart positions one at each side ofthe splice region; and with the cable allowed to follow the path itwould follow in the absence of the molds through and between the molds,holding the molds fixed relative to one another in desired positionsaligned with one another that they will occupy in the finished closure;and molding the ends while holding said molds in said positions.

Preferably, the molds are held in their aligned positions by a rigidclamping bar which is positioned axially across the cable splice and isclamped to each mold.

The invention also includes a low pressure molding apparatus for moldingplastic ends of a gas pressurizable closure, one axially at each side ofa splice region of a telecommunications cable, the apparatus comprisingtwo molds, each for molding one of the plastic ends, a rigid moldclamping bar, and locking means for securing the molds in spaced-apartpositions to the clamping bar and in axial alignment with one another.

With the above-described method and use of the apparatus, as the cablefollows its natural (i.e. the path it would follow the absence of themolds) path during the formation of the plastic ends and with the moldsdisposed in aligned positions, then there is no movement of the cablenor of the ends after the molding procedure and thus no distortion ofthe assembled enclosure takes place.

One embodiment of the invention will now be described by way of example,with reference to the accompanying drawings, in which:

FIG. 1 is a side elevational view, partly in cross-section of a gaspressurizable closure surrounding a splice region of cable;

FIG. 2 is a view on the end of the closure taken in cross-sectionthrough the cable along line II--II in FIG. 1;

FIG. 3 is a cross-sectional view taken along line III--III in FIG. 1 ofpart of the closure to show a detail;

FIG. 4 is a view in the direction of arrow IV in FIG. 3;

FIG. 5 is a view in the direction of arrow V in FIG. 1;

FIG. 6 is a cross-sectional view through a molded plastic end of theclosure;

FIG. 7 is a view similar to FIG. 1 of a modification of the embodiment;

FIG. 8 is an end view of an end of the closure of the modification takenin cross-section through the cable along line VIII--VIII;

FIG. 9 is a cross-sectional view through a mold used for molding aplastic end during the making of the closure of FIG. 1;

FIG. 10 is a view of the mold in the direction of arrow X in FIG. 9 andwith end seals removed for clarity;

FIG. 11 is a plan view of a sealing member used as part of a seal forsealing the ends of the mold;

FIG. 12 is a view similar to FIG. 10 and showing the sealing members inposition for molding a plastic end around the cable to provide theconstruction shown in FIG. 1;

FIG. 13 is a view similar to FIG. 12 with the sealing members adjustedin position and for making a plastic end according to the modificationshown in FIGS. 6 and 7;

FIG. 14 shows the assembly of the molds in spaced-apart positions upon acable during molding of the end caps;

FIG. 15 is a plan view of part of a rigid mold locking bar holding themolds in aligned positions; and

FIG. 16 is a view of part of the locking bar in the direction of arrowXVI in FIG. 14.

As shown by FIG. 1, two end sections 10 and 12 of pressurizable cableshave their conductors 14 and 16 extending outwardly beyond the ends ofthe cable jackets and sheaths. Each conductor of one cable is connectedto a conductor of the other cable to form a splice 18. Each splice andany bare conductor ends leading to it are electrically isolated fromother splices in conventional fashion with insulating wrapping material.

The splice region 20 formed along the axial lengths of the cables by thesplices 18 is provided with a gas pressurizable closure 22. As can beseen from FIG. 1, the closure 22 comprises two molded plastic ends 24which are spaced-apart one at each axial side of the splice region andsurround the cable end sections 10 and 12. The closure also includes asheath means 26 which is formed into substantially cylindrical conditionfrom a flexible sheet material such as steel which is wrapped around thetwo plastic ends to form a sleeve. As will be described, the sleeve issealed to each of the plastic ends 24 and the closure 22 is generally ofa construction such as is described in U.S. Pat. No. 4,581,480, issuedApr. 8, 1986 and entitled "Cable Encapsulation And Strain Relief" in thename of L. J. Charlebois.

To discuss the closure 22 in greater detail, each plastic end 24 has amain or large diameter disc-shaped section 28. This section 28 has anannular groove 30 within which is disposed a compressible plastic seal32 which is also sealed against the inside surface of the shroud means26. Extending from each side of the section 28 is an axial extension 34which, as is clear from FIGS. 1, 2 and 5 is of oval or elliptical shapein axial view for reasons to be discussed.

The two plastic ends 24 are connected together by two tensile strengthmembers 36 (see particularly FIG. 5) which are either steel bars ortubes extending between and screw-threadedly connected to screw-threadedstuds 38 which are molded integrally with the inwardly facing extensions34 and extend therefrom for securing to the bars 36. The tensile members36 and studs 38 are omitted from FIG. 1 to show the cable end sectionsin more detail. As described in the aforementioned U.S. Pat. No.4,581,480, the bars and studs act to ensure that tensile loads such asare produced in the cable do not cause the cables and thus the plasticends to pull apart. As discussed in the latter mentioned application,such an arrangement is particularly useful in the case of aerial cable.

The sheet forming the shroud means 26 has side edges 40 which are bentto form a U-shape as shown in FIG. 3, and the bases of the two U-shapesoppose each other and hold between them two axially extending seals 42for fluid tightly sealing the confronting edges of the sheets. To holdthe edges sealed together, arms 44 of each U-shape increase in lengthfrom one end of the sleeve towards the center of the closure and metallocking devices 46 are provided of C-shaped cross-section and also oftapering shape as shown by FIG. 4. Each device 46 conforms to thecombined shape of the opposing arms 44 and is mounted upon the sideedges 40 from an end of the sleeve as shown by FIG. 4, so as tointerlock with the U-shaped configuration. The locking devices force theedges 40 together so that they seal upon the seals 42. Securing pins 48are then inserted through aligned holes through the locking devices 46and the U-shaped edges 40 to hold the assembly together. The plasticends and the shroud means then provide an enclosed chamber 50 whichsurrounds the splice region and which is sealed from ambient atmospherewhile also providing a substantial seal to prevent pressurized gasesfrom escaping from within the arrangement. As shown by FIG. 6, eachplastic end 24 is provided with a strain relief device which is inseries with the bars 36 in transferring tensile loads from one cable tothe other. This strain relief device comprises a strap member 50 whichis bent around each of the cable end sections 10 and 12 and has flanges52 upstanding from a base 54 which contacts the cable. Each of the basesis formed with a piercing means in the form of prongs (not shown) whichproject into the cable jacket to hold the base in position as theplastic ends are molded in position, the flanges then becoming embeddedin the material of the encapsulations formed by the plastic ends. Thus,after manufacture, if any tensile load is placed along the enclosedsplice region then this load is taken from each cable jacket through theprongs into the base of the strap member and then from the flanges 52into the plastic end. The tension is then transferred to the otherplastic end by the bars 36. The structure of the strain relief device isdescribed in more detail in copending U.S. Pat. No. 4,581,480 asreferred to above.

Within each of the plastic ends 24, there is disposed a seal arrangementto prevent pressurized air from escaping from the chamber 50 along theinterfacial region between the associated cable and the plastic end.This seal acts effectively to seal between the jacket surface and theplastic end in a case where a single jacket is provided upon a cable. Inthis embodiment however each cable is formed with two jackets 58 and 60,one disposed within the other. In addition to preventing the pressurizedair from escaping to ambient atmosphere, it is also necessary to preventthe air from escaping along the cable itself, i.e. along the outsidesurface of the inner jacket 60 at its interface with any surroundinglayer of material. To provide the effective seal, therefore, and asshown by FIG. 6, the outer jacket 58 is removed for a further distancealong each of the cables so that the inner jacket 60 projects furthertowards the splice region. As is then shown, the end 62 of the jacket 58terminates within the plastic end and a seal 64 is provided around eachof the jackets 58 and 60. Each seal is of a construction described inU.S. Pat. No. 4,570,032, issued Feb. 2, 1986 and entitled "SealingClosure For A Cable Splice" in the names of L. J. Charlebois and K. H.Dick. As described in the latter application, each seal 64 comprises aninner wrapping 66 of a material which is deformable so that undercompression it will intimately engage the surface of the jacket so as toform a first seal with the jacket. Such a material for the inner layeris an ethylene-propylene rubber. An outer layer 68 which is wrappedaround it, needs to be a resilient tape material which is stretched verytightly so as to provide the required compressive force upon the layer66. This outer layer may be a neoprene rubber tape or that known as "DRTape" in the telecommunications cable industry. With this construction,because the layer 66 in the final structure is compressed, it forms apermanent compressive seal against the outer surface of its respectivejacket, and the outer regions of the layer 66 which form an interfacewith the encapsulation or plastic end 24 are bonded thereto during theencapsulation process by heat softening of the ethylene-propylenerubber. The outer layer 68 is axially narrower than the layer 66 so asto provide interfacial regions of the layer 66 with the encapsulation atthe edges of layer 66. It follows that when the encapsulation of theplastic end is formed by a molding process, to be described, then a sealis provided by each seal 64 thereby preventing the escape of pressurizedgas from the chamber notwithstanding that the encapsulation itself isnot bonded to the jacket of either of the cables as will be discussedbelow.

As is shown by FIG. 2, each of the cable end sections 10 and 12 passessubstantially concentrically through its plastic end 24. However, theplastic end is formed in such a way as to enable more than one cable toextend through it. For instance, in the modification shown in FIGS. 7and 8, a cable 70 passes completely through the closure 22 fromend-to-end and is opened by removal of the jacket and sheath along theregion 72 to reveal conductors of the core to enable a service cable 74to have its conductors spliced to certain conductors of the cable 70.The cable 70 proceeds through the plastic end 22 on the right-hand sideof FIG. 7 in the manner shown in the first embodiment for cable endsections 10 and 12. However, the cables 70 and 74 pass through theplastic end on the left-hand side of FIG. 7 in spaced-apart positions,as shown by FIG. 8, and each cable is surrounded with seals similar toseals 68 described in the first embodiment to prevent pressurized airfrom escaping along the outsides of the cables from chamber 50. Thus thecables, in passing through the plastic end 24, lie in the relationshipshown by FIG. 8. As can be seen, the oval or elliptical shape of theextensions 34 allow for such an arrangement of cables disposed in spacedpositions through the molding and substantially on the major axis of theprojections.

The plastic ends 24 as described in the embodiment and in themodification, are each molded within a mold shown by FIGS. 9, 10, 11, 12and 13. As shown in FIGS. 9 and 10, a mold 80 is a low pressure moldoperating below 20 psi and has two mold halves 82 and 84 hinged at oneside 85 (by a hinge not shown). As shown in the section in FIG. 9, themold halves 82 and 84 have a cavity with a central large diametersection 86 for forming the disc-shaped section 28 of a plastic end. Thecavity also comprises two cavity sections 88 at each side of the section86 for forming the extensions 34 on the plastic end. Each mold half 82and 84 is formed by two parts 90 and 92 which are bolted together bybolts 94 passing through annular flanges 96 which, together with anannular ring 98, forms the large diameter section 86. The annular groove30 in a plastic end is formed by an annular insert 100 fitted into thering 98 as shown in FIG. 9. The mold parts are made from metal and thesurfaces of the parts forming the mold cavity have a thermallyinsulating coating of approximately 0.010 inches thickness. This coatingis an epoxy resin, but alternatively could be formed from otherthermally insulating material such as polytetrafluorethylene.Alternatively, strips of polyvinylchloride may be used as the coatingwith a suitable adhering material disposed between the polyvinylchlorideand the metal surface to prevent the coating from stripping from thesurface. Also, as shown in FIG. 9, the mold has an orifice 102 in one ofthe flanges 96 for accepting a withdrawal pin 104 which holds a metaltubular insert 106 in a position extending across the recess 86 of themold cavity. This insert is for providing a passage through thedisc-shaped section 28 of a finished plastic end 24 for the purpose ofpressurizing the inside of the chamber 50 or for attaching an instrumentfor measuring the gas pressure within the chamber. At each end of themold there are provided two holes 108 (FIG. 10) which are formed at theparting line between mold halves and flank an orifice in the mold at theends of the cavity section 88 as shown in FIG. 9. These two holes arefor accepting the studs 38 (see FIG. 4) which pass into the extensions34 of the plastic end. A local thickening 110 of the mold is providedfor aligning the studs 38 correctly during the molding process.

Each of the mold halves 82 and 84 is also provided at its ends withaxially aligned tapering flanges 112 as shown by FIGS. 9 and 10. At eachmold end, flanges are diametrically opposed from one mold half to theother and are provided at their tapered extremities with outwardlyturned side flanges 114. The flanges 114 of each mold half are axiallyaligned (FIG. 9) and each of these flanges is formed with two spacedrecesses 116 (FIG. 10) which are symmetrically disposed with regard to avertical centerline of the mold. The use of these recesses will bediscussed below. With the mold closed, the diametrically opposed flangesprovide a planar end face for each mold end (FIG. 9).

The aluminum mold shown in FIGS. 9 and 10 is also equipped at each endwith a seal which is not shown in FIG. 10 and is shown at one end onlyof FIG. 9. As shown in FIGS. 11, 12 and 13, the seal at each end of themold comprises two planar sealing members 118 each of which, in planview, has a pentagonal-shaped body (FIG. 11). This shape produces fiveedge regions 120, 122, 124, 126 and 128 each of which is formed withsubstantially semi-circular sealing edges which are of differentdiameter or the number and/or diameter of which is different from oneedge region to the other. For instance, for sealing around cable endsections 10 or 12, as shown in the first embodiment, the edge 126 isprovided for this purpose. As shown in FIG. 11, this edge is formed witha single semi-circular sealing edge 130. However for the formation ofthe modification described with reference to FIGS. 7 and 8, the edgeregion 122 is formed with two semi-circular sealing edges 132 and 134which are provided one for each of the cables 70 and 74. Each sealingmember 118 is formed with a central orifice 136, and means in the formof a bolt and nut arrangement 138 (FIGS. 12 and 13) is used for mountingeach of the sealing members upon the planar end face of its respectivemold half by passage of the bolt through the orifice 136 and through acorresponding orifice 140 in the mold half (see FIGS. 9 and 10).

In use, each of the sealing members is rotatably movable upon itsmounting so as to present any one of the edge regions in an operatingposition facing across the junction of the mold halves so that it cancooperate with a corresponding edge region of its associated sealingmember for sealing completely around a cable or cables issuing from themold cavity. For instance, as shown in FIG. 12, the edge regions 126oppose each other along the junction of the mold halves to seal by meansof the sealing edges 130 around either of the cables 10 or 12 asdescribed in the first embodiment. Alternatively as shown in FIG. 13,the sealing members may be rotated to a position in which the edgeregions 122 oppose each other with the sealing edges 132 and 134 of thetwo members coacting to seal around the two cables 70 and 74. The otheredge regions 120 and 124 are used also for sealing around two cablesissuing from the mold cavity in a case where these cables are ofdifferent diameters from those described in the modification to theembodiment. The edge regions 128 are used for sealing around certaindiameters of three cables issuing from the mold cavity. Thus it is clearthat the sealing members of the invention, and as described in thisembodiment, provide a plurality of sealing edge regions with differentrequirements for sealing around cable diameters and numbers of cablesissuing from the mold cavity. As a result, less seals or sealing membersare required to be carried by a splicing operator into the field thanwould be the case if single and individual seals were to be used as inconventional practice for sealing in molds.

As shown in FIGS. 9, 12 and 13, the outside surfaces of the sealingmembers are covered with a reinforcing member in the form of stiffeningplate 142 which is shaped appropriately to fit around the sealing edges.The plate is also secured in position by the bolt arrangement 138.

In the molding of each plastic end 24, mold 80 is equipped with theinsert 106 if this is required and a layer of ethylene-propylene rubbertape is wrapped around a groove 143 in the insert for the purpose ofsealing the insert to the molded article to prevent pressurized air fromescaping. After location of the seals 64 and the strap member 50 aroundthe cable end sections at each side of a completed splice region 20, asin the embodiment, the molds are located in position at each side of thesplice region. Each mold is filled by passing molten polyethylenematerial into the mold cavity through an inlet (not shown) and, as themold fills, the molten material contacts the insulating coating on themetal surface as it flows through the cavity. It has been found thatwith the use of the insulating coating upon an aluminum mold, then forthe particular size of plastic end which is being made in theembodiment, about 20 minutes is sufficient for the molten material tocool and harden sufficiently to allow for removal of the mold. This timefactor is satisfactory from a manufacturing point of view. Removal ofheat from the mold cavity is initially resisted by the insulatingcoating but quick withdrawal of heat takes place immediately after theheat passes into the aluminum. Hence, the combination of the coatingwith the aluminum acts as a combined thermal insulation and heat sinkarrangement which is satisfactory for withdrawing heat from the materialat the required rate. Also, because of the arrangement of the insulatingcoating within the mold, upon the molten material contacting the coatingas it flows through the mold cavity, then heat is not removed from theimmediate surface of the molten material immediately it contacts theinsulation as would be the case if it contacted the bare uncoveredaluminum. In view of this, the insulating coating allows sufficient timefor the material to flow into intimate molding contact with the coatingforming the mold surface before solidification of the surface regiontakes place. Hence, all of the parts of the finished article are smootheven though the operation is performed by low pressure molding. Inparticular, the molding material contacting the insert 100 also isprovided with a smooth molded surface. This material forms the groove 30in the plastic end and the smooth surface is satisfactory for sealingpurposes against the sealing ring 32 which fits within the groove. Itfollows therefore that with low pressure molding techniques, i.e. below100 psi and preferably below 20 psi, that the article is moldedintimately into contact with the mold surface thereby enabling a smoothmolded surface to result. Hence, smooth sealing surfaces may be providedby this technique.

During molding, the molten material is passed into the mold cavity at atemperature of about 204° C. The heat dissipates through the moldsufficiently quickly to prevent softening of the jacket material andfusing the jacket to the encapsulation. This is the case even though thejacket is itself formed from polyethylene. Choosing a different gradepolyethylene for the molten material assists in prevention of thisfusing action. However, there is sufficient heat retention over asufficiently long period to soften the edges of the layers 66 of seals64 and which project beyond the layers 68. These edges of layers 66 thenform a bond with the encapsulation to provide a seal.

Appropriately, the two plastic ends 24 are molded into positionsimultaneously. This is effected according to the invention by providingtwo molds 80 which are disposed at their required distances apart ateach side of the splice region as shown in FIG. 14. The two molds areheld in their desired positions axially aligned with one another by arigid mold clamping bar 144. As shown in greater detail in FIGS. 14 and15, the clamping bar 144 is in the form of a rigid U-shaped steel barwhich is positioned to extend across the flanges 114 at one side of thetwo molds. The bar 144 has abutment means in the form of twospaced-apart abutment members 146 which provide transverse recesses 148facing towards adjacent ends of the bar. These recesses are spaced-apartso as to hold a flange 114 of one of the mold halves therein and controlthe distance apart of the two molds 86. The bar has locking means forsecuring the molds in the spaced-apart positions with a flange of eachmold in a recess 148 and against an associated member 146. This lockingmeans comprises two manually operable, over center, locking devices 150each provided with a handle 152 pivoted at position 154 to a bracket 156secured to the bar. The handle 152 has a U-shaped locking member 158pivotally attached to it and adjacent ends of the member by a cross-yoke160 through which screw-threaded ends of the member 158 pass, thecross-yoke held in a desired position by lock nuts 162. The base 164 ofthe locking member is locatable beneath a narrow section 166 of theouter flange 114 and formed between recesses 116 and this base islocated in a locking or clamping position (FIG. 16) with the handle 152in the over center position shown. Arms 168 of locking member 158 passthrough recesses 116.

The clamping bar is located in position as shown in FIGS. 14 and 15 inwhich the flanges 114 at that side of the complete assembly of molds andcables all are held firmly against a planar mold flange engagingsurface, i.e. the undersurface 170 of the bar, and are retained in theiraxial positions apart in a mold locking position. This securing of themolds in this fashion ensures that they are axially aligned in therequired manner and in their desired positions. If it is found thatthere is any slight movement of either of the molds out of the alignedpositions, then another locking bar 144 (not shown) may be located onthe other side of the assembly to hold it more rigidly. With the moldsdisposed in these aligned positions for the molding operation, the cableor cables passing through them may follow the natural path of curvaturethrough and between the molds as shown in FIG. 14. Hence after themolding operation has been completed, there is no tendency for thecables to return towards a normal curved condition which would have theeffect of displacing the plastic ends 24 from their aligned positions inwhich they are molded. Therefore there is no twisting force imposed uponthe plastic ends which would tend to destroy any seal between theplastic ends and the shroud means 26 through the annular seals 32. Thismethod of molding the two plastic ends together therefore removes anypossibility of any sideways or twisting forces being applied to thefinished closure which would have the tendency to distort the closureand break the gas pressurizable arrangement.

What is claimed is:
 1. A method of a gas pressurizable closure for asplice region of a telecommunications cable in which the closure hasaxially spaced molded plastic ends and a bridging shroud means, themethod including molding the ends in position by disposing two molds forthe ends in axially spaced-apart positions, one at each side of thesplice region; and with the cable allowed to follow the path it wouldfollow in the absence of the molds through and between the molds,holding the molds fixed relative to one another in desired positionsaligned with one another that the spaced ends will occupy in thefinished closure, and molding the ends while holding the molds in saidpositions and locating the shroud means in position extending betweenthe plastic ends and sealed thereto with the cable still following saidpath, such that there is no twisting force imposed upon the plastic endswhich would tend to destroy the seal between the plastic ends and theshroud means.